Free convection is the area of fluid mechanics dealing with the motion of a fluid arising from temperature differences within the fluid. This contrasts with forced convection[?].
A typical example is hot air rising off a on oil radiator, and then circulating around a room.
... 6.3% from 18 to 24, 32.3% from 25 to 44, 21.1% from 45 to 64, and 11.8% who are 65 years of age or older. The median age is 37 years. For every 100 females there are ...